linux-kernel - Re: [PATCH RFC 2/2] mm: Use pte markers for swap errors

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Message-ID: <6357f4ab-32f1-3654-9a18-deb4f5364a92@huawei.com>
Date:   Sat, 29 Oct 2022 10:49:11 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Peter Xu <peterx@...hat.com>, <linux-kernel@...r.kernel.org>,
        <linux-mm@...ck.org>
CC:     Huang Ying <ying.huang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        HORIGUCHI NAOYA <naoya.horiguchi@....com>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH RFC 2/2] mm: Use pte markers for swap errors

On 2022/10/25 4:48, Peter Xu wrote:
> PTE markers are ideal mechanism for things like SWP_SWAPIN_ERROR.  Using a
> whole swap entry type for this purpose can be an overkill, especially if we
> already have PTE markers.  Define a new bit for swapin error and replace it
> with pte markers.  Then we can safely drop SWP_SWAPIN_ERROR and give one
> device slot back to swap.
> 
> We used to have SWP_SWAPIN_ERROR taking the page pfn as part of the swap
> entry, but it's never used.  Neither do I see how it can be useful because
> normally the swapin failure should not be caused by a bad page but bad swap
> device.  Drop it alongside.
> 
> Signed-off-by: Peter Xu <peterx@...hat.com>

Thanks for doing this. I have been waiting this for a "long" time. ;)
With changing the name of PTE_MARKER_SWAP_ERROR proposed by David, this
patch looks good to me.

Reviewed-by: Miaohe Lin <linmiaohe@...wei.com>

Thanks,
Miaohe Lin